The lower gastro-intestinal tract is the continuation of the digestive tract after the stomach and. It is composed of the small intestine (subdivided into the jejunum and the ileum , which is 4 to 7 meters long, the colon (also named the large intestine), the rectum and the anus.
The small intestine begins at the angle of Treitz and ends up in the colon at the ileo-cecal valve. Its function is to reabsorb sugar, proteins, fats, minerals, vitamins and water.
The colon is about 1.5 meters long. It begins at the level of the right iliac fossa, then is subdivided into the ascending colon (right part), the transverse colon (part under the ribs), the descending colon (left part), and then into the sigmoid colon (which is located in the left iliac fossa) which continues to the rectum. The colon completes the absorption of water and the constitution of the stool.
The rectum is about 15 cm long and serves as a reservoir for the stool, regulating the defecation mechanism.